JP2006215331A - Developing device and image forming apparatus using the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that reduces the problems of an overflow system and steadily discharges an excess of developer while minimizing waste, and to provide an image forming apparatus. <P>SOLUTION: A developer discharging section 8 has a discharging hole 28 made in the wall of a passage along which developer is circulated and conveyed. A developer stirring part 30 having developer stirring force that is greater than the other conveyance area is disposed in the upstream of the discharging hole 28 in the direction of the developer circulation and in the downstream of a developer supply position from which developer is supplied to a developing roller 21 or a developer replenishment position 3 replenished with toner and developer by cartridges 4 and 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a two-component developing device and an image forming apparatus using the developing device.

  In image forming apparatuses such as printers, copiers, facsimiles, and multifunction machines having at least two of these functions, a developing device that develops an electrostatic latent image using a two-component developer composed of toner and carrier is often used. Yes. Since this type of image forming apparatus consumes toner together with image formation, it normally supplies toner in a container sequentially, and when the toner in the container runs out, it is replaced with a new toner container to replenish the toner. .

  On the other hand, the carrier is not consumed, but its performance deteriorates with the number of image formations. Therefore, it is necessary to replace the carrier every certain number of image formations. As a general method of carrier replacement, a method in which a dedicated service person replaces a carrier in a copier and a method in which a developing device incorporating a carrier is replaced with a new unit for a printer are generally used. is there. However, if it is continuously used until the carrier deteriorates, there is a problem that the image quality at the beginning and at the time of deterioration are clearly different, and many recorded materials with poor image quality are provided.

  Therefore, recently, a method has been proposed in which a stable image can be continuously obtained by mixing a carrier with the toner to be replenished in advance, sequentially replenishing the toner and carrier to the developing device, and collecting excess developer. And has been implemented. Furthermore, it has been proposed that the toner and the carrier are independently supplied from containers that separately store the toner and the carrier.

JP 2000-81787 A

  In such a developing device that replenishes the carrier little by little, in order to maintain the toner concentration of the device within a certain range, it is necessary to collect excess developer. As a method for discharging the developer, as described in Patent Document 1, in the overflow method and the revolver developing method in which a discharge hole is provided at a predetermined height of the wall surface of the developing casing and the excess developer is overflowed and discharged. A method of opening and closing the shutter of the discharge hole using gravity is known.

  However, when applied to stationary development devices such as tandem color machines that have become mainstream in recent years, the former overflow method, which can be used with a relatively simple configuration, has become the mainstream because it cannot be applied due to the limitation of the latter revolver development method. ing.

  In addition to toner replenishment, the carrier is replenished, and the disadvantage is that the excess developer is discharged from the developer discharge hole by overflow. The developer in the developing device is a mixture of toner and carrier. Even if the carrier amount inside the apparatus is the same, the volume of the mixture increases or decreases depending on the toner mixing ratio (toner concentration), and the volume increases when the toner concentration (usually about 5% to 12%) is high. Sometimes the volume decreases. When discharging is performed in the state where the volume is changed in this way, a large amount of developer is discharged when the toner concentration is high, and when the toner concentration is low, discharging is not performed even when the carrier is replenished. There is a problem that the amount of carriers held inside also fluctuates.

Further, as described above, since the toner tends to be discharged when the toner concentration is high, there is a problem that a large amount of toner is discharged simultaneously with the discharge of the carrier.
Furthermore, depending on the positional relationship between the toner or carrier replenishment port and the developer discharge hole, there is a problem in that waste is caused that the supplied new toner or carrier is immediately discharged from the discharge hole without being used.

  Further, the volume of the developer varies depending on the charge amount of the developer as well as the change in the toner density. When the charge amount is high, the developer volume increases (decrease in bulk density), and when the charge amount is low, the developer volume decreases. Therefore, there is a problem that the discharge amount also changes depending on the charge amount change.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device and an image forming apparatus that alleviate the problems of the overflow method described above and enable stable discharge of excess developer with little waste.

  In order to achieve the above-described object, the present invention circulates and conveys a developer in a development carrier disposed opposite to an image carrier and a development casing, and supplies the developer to the development carrier in the middle of the conveyance. A developer circulating and conveying means; a developer replenishing device for replenishing the developer to the developing device from a developer accommodating portion provided outside the developing device; and a developer discharging means for discharging excess developer in the developing device. In the developing device, the developer discharge means has a discharge hole provided in a wall surface of a passage for circulating and transporting the developer, and is developed on the upstream side of the discharge hole in the developer circulation direction and developed on the developer carrier. A developer agitating section having a developer agitating force higher than that of other transport areas is provided between the developer supply position for supplying the developer or the downstream side from the developer replenishment position where the developer is replenished from the developer storage section. It is characterized by that.

  According to the present invention, in the developing device according to claim 1, the developer agitating unit reduces the transport force of the developer transport member that constitutes the developer circulation transport unit, so that the developer is discharged from other transport regions. It is effective when the passage time is extended.

  Further, in the present invention, when the developer conveying member is a screw, and the developer agitating unit is provided with a planar member extending substantially perpendicular to the screw shaft by cutting off the screw blades in the screw, It is effective.

  Furthermore, in the present invention, the developer conveying member is a screw, and the developer agitating portion is provided with a linear or planar member extending substantially parallel to the screw shaft on a screw blade of the screw. And effective.

  Furthermore, in the present invention, the developer circulation conveying means includes a first screw adjacent to the developer carrying member, and a second screw that conveys the developer in a reverse direction in parallel with the first screw, It is effective when the discharge hole is provided at the downstream position of the second screw.

  In order to achieve the above object, the present invention provides an image forming apparatus for developing an electrostatic latent image formed on the surface of an image carrier using the developing device according to any one of claims 1 to 5. The developer discharging means has a discharge hole provided in the wall surface of the passage for circulating and conveying the developer, and a shutter for opening and closing the discharge hole, and the opening and closing of the shutter is controlled by the shutter control means. It is characterized by.

  In the present invention, the toner for detecting the toner adhesion amount per unit area developed on the image carrier from the developing device or the toner adhesion amount per unit area transferred from the image carrier to the transfer body. It is effective to provide an adhesion amount detection means, and when the shutter control means normally closes the shutter and the shutter opens when the detection result of the toner adhesion amount detection means falls within a predetermined range.

  Further, according to the present invention, there is provided toner density detecting means for detecting the toner density of the developer in the developing device, the shutter control means normally closes the shutter, and the detection result of the toner density detecting means falls within a predetermined range. When the shutter is opened, it is effective.

  Furthermore, the present invention is effective when the shutter control means opens the shutter when the detection results of the toner adhesion amount detection means and the toner density detection means both fall within a predetermined range.

  Furthermore, the present invention is effective if the opening operation of the shutter is prohibited from when the developing device is not in operation until after the developing device has been continuously operated for a predetermined time.

  According to the first aspect of the present invention, the developer discharge means has a discharge hole provided in the wall surface of the passage for circulating and conveying the developer, upstream of the discharge hole in the developer circulation direction, and the development carrier. A developer agitating unit having a developer agitating force higher than that of the other transport areas, between the developer supply position for supplying developer to the developer supply position or the developer replenishment position downstream from the developer supply position. Because it is provided, even if the developer fluidity changes depending on the environment and the charge amount, the change in developer bulk density, that is, the change in developer amount in the developing device can be suppressed to the minimum, and the toner density control stability , Image stability can be improved.

  According to the second aspect of the present invention, the developer agitating portion is a portion in which the developer conveying member constituting the developer circulating and conveying means is reduced in the conveying force so that the developer passage time is longer than that in the other conveying regions. Further, the stirring effect of the developer stirring unit can be enhanced.

  According to the third aspect of the present invention, the developer conveying member is a screw, and the developer agitating portion is provided with a planar member that cuts off a screw blade in the screw and extends substantially at right angles to the screw shaft. Further, the stirring effect of the developer stirring unit can be enhanced.

  According to the configuration of claim 4, the developer conveying member is a screw, and the developer agitating portion is configured by providing a linear or planar member extending substantially parallel to the screw shaft on the screw blade of the screw. Therefore, the stirring effect of the developer stirring unit can be enhanced.

  According to the configuration of claim 5, the developer circulation conveying means includes a first screw adjacent to the developer carrying member, and a second screw that conveys the developer in a reverse direction in parallel with the first screw, Since the discharge hole is provided at the downstream position of the second screw, the developer stirring unit can be easily installed in the region of the second screw.

  According to the configuration of the sixth aspect, in the image forming apparatus for developing the electrostatic latent image formed on the surface of the image carrier using the developing device according to any one of the first to fifth aspects, the developer discharge is performed. The means has a discharge hole provided in the wall surface of the passage for circulating and conveying the developer, and a shutter for opening and closing the discharge hole, and the opening and closing of the shutter is controlled by the shutter control means. While stabilizing and eliminating wasteful discharge, the above-mentioned effects can be obtained more reliably.

  According to the configuration of the seventh aspect, the toner adhesion amount per unit area developed on the image carrier from the developing device or the toner adhesion amount per unit area transferred from the image carrier to the transfer body is detected. A toner adhesion amount detection means is provided, and the shutter control means normally closes the shutter, and the shutter opens when the detection result of the toner adhesion amount detection means falls within a predetermined range, so that the developer discharge amount can be stabilized. .

  According to the configuration of the eighth aspect, the toner density detecting means for detecting the toner density of the developer in the developing device is provided, the shutter control means normally closes the shutter, and the detection result of the toner density detecting means falls within a predetermined range. Since the shutter is opened when the developer is discharged, the developer discharge amount can be stabilized.

  According to the configuration of the ninth aspect, the shutter control means opens the shutter when the detection results of the toner adhesion amount detection means and the toner density detection means both fall within a predetermined range, so that the developer discharge amount is stabilized. Can be

  According to the configuration of the tenth aspect, since the opening operation of the shutter is prohibited from the time when the developing device is not in operation until after the continuous operation of the developing device for a predetermined time, it is possible to prevent the developer from being discharged when the volume is unstable. it can.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view showing the overall configuration of the developing device. Reference numeral 1 denotes a photosensitive drum as an image carrier, and an electrostatic latent image is formed on the surface by a charger and an optical writing device (not shown). Reference numeral 2 denotes a developing device, which develops the electrostatic latent image formed on the photosensitive drum 1 with toner to form a visible image. A replenishing port 3 for supplying toner and a carrier provided in the developing device 2 replenishes the toner stored in the toner cartridge 4 to the developing device 2 little by little via the toner replenishing path 6. As for the carrier, the carrier alone contained in the carrier cartridge 5 or a developer mixed with a small amount of toner is replenished to the developing device 2 little by little via the carrier replenishment path 7. The toner and the carrier in each cartridge are omitted, but they are replenished by a general screw method or a transport function in which a pump mechanism for supplying powder and an air supply means are arranged. .

  Reference numeral 12 denotes a toner concentration sensor, which is a sensor that detects the toner mixing ratio by measuring the magnetic permeability of the developer in the developing device 2. The mixing ratio of the toner with respect to the carrier of the developer in the developing device 2 is normally used in the range of about 5% to 12%, and the toner supply is controlled based on the output of the toner density sensor 12. . That is, in the toner replenishment, an appropriate toner density range is set based on the target image density in the electrophotographic image forming apparatus, and a stable image is obtained by replenishing the toner little by little so as to be within this range. Controlled.

  On the other hand, the carrier is replenished to the inside of the developing device 2 little by little based on the number of formed images or the operating time of the developing device 2. By adding a new carrier little by little, the charging performance of the carrier that gradually deteriorates is compensated, and the total charging performance of the total carriers in the developing device 2 is maintained above the limit value. With this configuration, stable image formation can be continued without the need for periodic carrier replacement (replacement) as in the prior art.

  Further, since the total amount in the developing device 2 increases when the carrier is replenished, it is necessary to discharge the remaining carrier to the outside of the developing device 2 due to the replenishment. Therefore, the developing device is provided with a developer discharge portion 8 for discharging the carrier. Then, the developer discharged to the developer discharge portion 8 is collected in the developer collection container 9 via the discharge conveyance path 10. A discharge hole 28 (shown in FIG. 2) is formed in the developer discharge portion 8 at a certain height, and excess developer in the developing device falls from the discharge hole 28 to the developer discharge portion 8 and is discharged. The

  Since the toner cartridge 4, the carrier cartridge 5, and the developer collection container 9 are detachably provided in the main body device, when the toner cartridge 4 and the carrier cartridge 5 are used up, the developer collection container 9 becomes full. Can be exchanged when

FIG. 2 is a diagram illustrating an internal configuration of the developing device 2, and FIG. 3 is a diagram of the interior of the developing device 2 as viewed from above.
2 and 3, the developing device 2 includes a developing roller 21 as a developer carrying member disposed opposite to the photosensitive drum 1 in a developing casing 20, a first screw 22 and a second screw 23 that circulate and convey the developer. Is provided. The two screws 22 and 23 have spiral fins called a conveyance auger and are arranged in parallel to each other. Between the first screw 22 and the second screw 23, there is provided a partition plate 24 whose both ends in the longitudinal direction serve as communication passages 25, 26, and the circulation transport means is constituted by the two transport screws 22, 23 and the partition plate 24. The developer is circulated in the direction of the arrow in FIG. 3, that is, in the counterclockwise direction in FIG. The developer conveyed by the first screw 22 is attracted and supplied to the developing roller 21 by a magnetic force. The developer sucked up by the developing roller 21 is made uniform in thickness by the doctor blade 27, and then the electrostatic latent image on the photoreceptor is developed with toner to form a toner image.

  The toner and carrier replenishment ports 3 are provided on the upstream side in the developer transport direction on the second screw 23, and the developer discharge portion 8 is provided on the downstream side in the developer transport direction on the second screw 23. The toner and carrier replenishing port 3 is set on the upstream side in the developer conveying direction on the second screw 23 so that the replenished toner can be further stirred until it reaches the developing roller 21. Further, the developer discharge portion 8 is generally near the center on the second screw 23. However, if the developer discharge portion 8 is located downstream in the developer transport direction, the toner supplied from the supply port 3 is immediately discharged. In addition, the developer agitating unit 30 described below can be easily installed in front of the discharge unit 8, that is, in the vicinity of the upstream side in the developer transport direction.

  The developer agitation unit 30 is a part having a configuration capable of sufficiently agitating the developer before being discharged from the discharge unit 8. When the developer stirring unit 30 is provided, even if the developer fluidity is lowered due to the environment, the toner charge amount, and the toner concentration, the fluidity is always kept good by the stirring unit. Changes in the amount of carriers in the developing device due to (volume) changes can be suppressed to a minimum, and toner density control stability, image stability, and the like can be improved. The developer agitating unit 30 is located upstream of the developer discharge unit 8 in the developer circulation direction and between the developer supply position for supplying the developer to the developing roller 21 or the downstream side of the toner and carrier supply port 3. Can be provided. More preferably, by providing a developer stirring portion 30 having a developer stirring force higher than that of the other transport areas adjacent to the upstream side of the discharge hole 28 in the developer circulation direction, it is caused by a change in bulk density (volume) of the developer. The change in the carrier amount in the developing device can be suppressed to the minimum, and the effect of improving the stability of toner density control, the stability of the image, etc. can be obtained with certainty.

  The shape and dimensions of the developer agitating unit 30 are different depending on the type of developer and the inside of the machine used so that the agitating ability can be recovered to the extent that it can recover a decrease in the charge amount due to leaving or in a high humidity environment or a decrease in fluidity due to environmental fluctuation. What is necessary is just to set suitably according to an environment. In particular, with respect to charging, it is necessary to have a stirring ability that reaches or is close to the saturation charge amount of the toner.

  The developer agitating unit 30 is configured so that it is provided on the outer periphery of the screw parallel to the axis as shown in FIG. 6, as shown in FIG. 6, and as the axis parallel plane member 32 as shown in FIG. The cylindrical wall 33 and the like have a high stirring effect (fluidity increasing effect) and are effective.

  Further, as shown in FIG. 4, if the spiral blade of the screw of the developer agitating unit 30 is cut out, the developer transfer force in the axial direction of this portion is reduced and the developer stays. By causing the developer to stay in the developer stirring section, the developer can be more sufficiently stirred (because of the long time during which the same developer is stirred), and the developer bulk density fluctuation can be further reduced.

  In this way, by providing the developer stirring unit 30 and suppressing the change in the bulk density of the developer just before discharging due to overflow, the stability of toner density control and the stability of the image can be ensured.

  FIG. 7 is a perspective view showing the overall configuration of a developing device according to another embodiment of the present invention. The difference from FIG. 1 is that a shutter 40 for opening and closing the discharge hole 28 of the developer discharge portion 8 is provided. is there.

  As shown in FIG. 8, the shutter 40 is supported by a hole provided in the side wall in which the discharge hole 28 is formed and a pin 41, and can be slid in the left-right direction in the figure. Is being energized. Reference numeral 43 denotes a solenoid provided on the apparatus main body side, which acts to pull the shutter 40 in the direction opposite to the arrow F when energized. In FIG. 8, the solenoid 43 is in an OFF state, and the shutter 40 is in a closed state. FIG. 9 shows a state in which the solenoid 43 is in an ON state and the shutter 40 is in an open state. Although the discharge hole 28 shown in the figure is a rectangular opening, the shape of the discharge hole may be circular, oval, or the like.

  As shown in FIG. 8, the shutter 40 is normally biased by the spring 42 in the closing direction as shown in FIG. 8, so that the shutter 40 is closed during operation of the developing device 2 alone or during maintenance. Therefore, the developer does not flow out. Further, since the shutter 40 is closed if the solenoid is OFF even when it is attached to the main body, the developer does not flow out even in a situation where the main body is inclined due to transportation or movement.

FIG. 10 is a diagram showing the output of the toner density sensor 12.
As shown in the figure, the toner concentration is detected by the characteristic that the output (V) of the sensor increases when the toner concentration decreases and the output decreases as the toner concentration increases. The toner density control range has an appropriate range (1N to 4N) corresponding to the desired image density. When the toner density falls within this appropriate range, the toner supply device is operated to supply toner to the developing device. Is controlled to do.

  Since the developer volume varies depending on the toner concentration, the excess developer is discharged by opening the shutter 40 when the toner concentration falls within a predetermined range (2N to 3N) within the appropriate range. Excess developer is discharged.

  FIG. 11 is a time chart for opening the shutter 40. When the toner density of the developer in the developing device 2 gradually decreases as the image is formed and reaches a predetermined range upper limit 2N, the shutter 40 is opened and the predetermined range is reached. Continue to open until below the lower limit of 3N. When the value falls below the predetermined range lower limit 3N, the shutter 40 is closed. Further, toner supply is performed when the toner density decreases and falls below the appropriate range 4N. In order to improve the dispersion into the developer, the supply is preferably carried out in small portions and in several batches. When the toner density rises after toner supply and falls within the appropriate range, the toner supply is stopped. When the toner density rises and falls within the predetermined range again, the shutter 40 is opened and the developer is discharged. When it rises and exceeds a predetermined range upper limit 2N, the shutter is closed. As described above, the excess developer is discharged when the toner concentration is within the predetermined range 2N to 3N, so that the change in the bulk density of the developer when the developer is discharged is minimized, that is, the carrier in the developing device. The amount can be constant. In addition, also in this embodiment, the developer can be discharged more stably by providing the developer stirring unit 30.

Here, when the carrier amount in the developing device 2 fluctuates, the following problems occur.
When determining the toner density by measuring the carrier density with a magnetic permeability sensor, even if the toner density does not fluctuate, if the carrier amount fluctuates, it will be erroneously detected as a toner density fluctuation. Becomes very unstable, and as a result, the image density fluctuates and becomes uncontrollable.

  When the carrier amount is increased, the driving torque of the conveying member is increased, the power consumption is increased, and the stress applied to the developer is increased to promote deterioration. When the amount of carrier increases beyond the stirring region of the conveying member (in the upper part), the replenishment toner in that portion is not sufficiently stirred, resulting in uneven density, background contamination due to insufficient charge amount, toner scattering, and the like. In other words, it is possible to solve the above problems by fixing the carrier amount.

12, 13 and 14 are diagrams for explaining another embodiment of shutter control.
Here, instead of the toner density, the shutter 40 is opened within a predetermined range of the toner charge amount.

  As shown in FIG. 12, the toner charge amount correlates with the toner adhesion amount per unit area on the photoreceptor. Although the toner adhesion amount on the photosensitive drum 1 is not shown, it can be detected by a conventionally known reflection type optical sensor (P sensor) or the like, so the toner charge amount is estimated from the detection result of the toner adhesion amount. Is possible. An operation example of opening the shutter according to the estimated change in the toner charge amount is shown in the time chart of FIG. The shutter 40 is opened when the toner charge amount of the developer in the developing device 2 gradually increases with the image formation and reaches the lower limit of the predetermined range, and is kept open until the upper limit of the predetermined range is exceeded. When the predetermined range upper limit 3N is exceeded, the shutter 40 is closed. When the toner charge amount decreases and falls within the predetermined range again, the shutter 40 is opened and the developer is discharged, and when the toner charge amount decreases and exceeds the lower limit of the predetermined range, the shutter is closed. By discharging the excess developer when the toner charge amount is within the predetermined range as described above, the change in the bulk density of the developer at the time of developer discharge is suppressed to the minimum, that is, the carrier amount in the developing device is reduced. Can be constant. Furthermore, also in this embodiment, the developer can be discharged more stably by providing the developer stirring unit 30.

  Factors that cause the toner charge amount to fluctuate in the developing device 2 include environmental humidity, developing device drive time, toner concentration, toner replenishment amount, deterioration of toner and carrier over time, and the like.

  FIG. 13 shows an example of the relationship between the driving and stopping times of the developing device 2 and the toner charge amount. As shown in the figure, the charging of the toner rises when the developing device 2 is driven, and the charge amount of the toner is reduced by being left after the driving of the developing device 2 is stopped. Since the developer is not agitated when the developing device 2 is stopped, the toner density cannot be measured accurately. Further, since the development cannot be performed and the toner adhesion amount cannot be measured, the above control cannot be performed. Therefore, the shutter 40 needs to be closed.

1 is a perspective explanatory view of an image forming apparatus showing an embodiment of the present invention. 1 is a schematic diagram illustrating a configuration of an image forming apparatus of the present invention. FIG. 3 is an explanatory cross-sectional view of the developing device shown in FIG. 2 as viewed from above. It is explanatory drawing of the developer stirring part which shows one Embodiment of this invention. It is explanatory drawing of the developer stirring part which shows other embodiment of this invention. It is explanatory drawing of the developer stirring part which shows other embodiment of this invention. It is a perspective explanatory view of an image forming apparatus showing another embodiment of the present invention. It is explanatory drawing which shows the shutter of a closed state. It is explanatory drawing which shows the shutter of an open state. 6 is a graph showing a relationship between an output of a toner density sensor and a toner density. 6 is a timing chart showing when the shutter is opened and closed based on toner density. 6 is a graph showing a relationship between a toner adhesion amount and a toner charge amount. 6 is a graph showing the relationship between the toner adhesion amount and when the developing device is driven. 6 is a timing chart showing opening and closing of a shutter based on a toner charge amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Developing apparatus 8 Developer discharge part 12 Toner density sensor 21 Developing roller 22, 23 Screw 24 Partition plate 28 Discharge hole 30 Developer stirring part 40 Shutter

Claims (10)

A developer carrier disposed opposite to the image carrier, a developer circulating and conveying means for circulating and conveying the developer in the developing casing, and supplying the developer to the developer carrier during the conveyance; and provided outside the developing device. A developing device having a developer replenishing device for replenishing the developer to the developing device from the developer storage unit, and a developer discharging means for discharging excess developer in the developing device;
Development in which the developer discharge means has a discharge hole provided in a wall surface of a passage for circulating and conveying the developer, and is upstream of the discharge hole in the developer circulation direction and supplies the developer to the developer carrier. A developer agitating section having a developer agitating force higher than that of other transport areas is provided between a developer supply position or a downstream side of a developer replenishment position where the developer is replenished from the developer storage section. Developing device.   2. The developing device according to claim 1, wherein the developer agitating unit reduces the conveying force of the developer conveying member constituting the developer circulating conveying means to make the developer passage time longer than the other conveying regions. A developing device characterized by the above.   3. The developing device according to claim 2, wherein the developer conveying member is a screw, and the developer agitating unit is provided with a planar member extending substantially perpendicular to the screw shaft by cutting off a screw blade in the screw. A developing device.   3. The developing device according to claim 2, wherein the developer conveying member is a screw, and the developer agitating unit is provided with a linear or planar member extending substantially parallel to the screw shaft on a screw blade of the screw. A developing device comprising:   3. The developing device according to claim 1, wherein the developer circulating and conveying means is a first screw adjacent to the developer carrying member, and a second screw that is parallel to the first screw and conveys the developer in the opposite direction. And the discharge hole is provided at a downstream position of the second screw. An image forming apparatus for developing an electrostatic latent image formed on the surface of an image carrier using the developing device according to claim 1.
The developer discharge means has a discharge hole provided in a wall surface of a passage for circulating and conveying the developer, and a shutter for opening and closing the discharge hole, and the opening and closing of the shutter is controlled by the shutter control means. An image forming apparatus.   7. The image forming apparatus according to claim 6, wherein a toner adhesion amount per unit area developed on the image carrier from the developing device or a toner adhesion per unit area transferred from the image carrier to the transfer body. An image is characterized in that toner adhesion amount detection means for detecting the amount is provided, the shutter control means normally closes the shutter, and the shutter opens when the detection result of the toner adhesion amount detection means falls within a predetermined range. Forming equipment.   7. The image forming apparatus according to claim 6, further comprising a toner density detecting unit that detects a toner density of the developer in the developing device, wherein the shutter control unit normally closes the shutter, and the detection result of the toner density detecting unit. The image forming apparatus is characterized in that the shutter is opened when a predetermined range is reached.   9. The image forming apparatus according to claim 6, wherein when the shutter control unit detects both the detection results of the toner adhesion amount detection unit and the toner density detection unit within a predetermined range. An image forming apparatus, wherein the shutter is opened. 10. The image forming apparatus according to claim 7, wherein the opening operation of the shutter is prohibited from a time when the developing device is not operated to a time after the developing device is continuously operated for a predetermined time. Forming equipment.

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